Map Windows Key to Activate KMenu

Open a Konsole window

Find the key to which Super_L (the Windows key comes up as Super_L) is mapped by running xev (it will open a small window that waits for your keyboard input and displays it in the console window where xev was started. Closing the window will cause xev to terminateCode:xev | grepSuper_L

The keycode above came from my keyboard. Please run xev to determine what your keycode is.

Create a file under ~/.kde/Autostart to remap the above discovered keycode to F13. I called my file win-key.sh as per the doc at Mepis (also Mepis mentioned mapping the keycode to the string Menu, but that did not work for me).

#!/bin/bash
xmodmap -e 'keycode 133 = F13'

Make the script you created in Step 3 executable:chmod+x ~/.kde/Autostart/win-key.sh

Execute the script manually (it will be executed every time you restart)~/.kde/Autostart/win-key.sh

The Windows key should now activate the KMenu.Remember, if you have programs using the Windows key as the Meta key then your programs will now be broken (I lied when I said I would only warn you once).
References: